Growing internet and data communications are resulting in the need for greater numbers and types of optical components within expanding optical networks. DWDM systems, or any system that utilizes light to transmit information, utilize a variety of components for creating, transmitting, manipulating and detecting light. Such optical device components, also referred to as optoelectronic or photonic components, often comprises at least a portion that is transmissive to light at particular wavelengths. Fibers and planar light guides are examples of passive light transmissive optical components within an optical network. However, light manipulators (components that modify, filter, amplify, etc. light within the optical network) also often have portions that are transmissive to light, as often do photodetectors and light emitters.
Regardless of the type of optical device component, it is usually desirable that a material is used that is highly transmissive to the wavelengths used to transmit information through the optical network. In addition to low optical absorbance, the material should preferably have low polarization dependent loss and have low birefringence and anisotropy, and low stress. It is also desirable that the material be easy to deposit or form preferably at a high deposition rate and at a relatively low temperature. Once deposited or formed, it is desirable that the material can be easily patterned, preferably directly patterned without the need for photoresist and etching steps, and preferably patterned with small feature sizes if needed. Once patterned, the material should preferably have low surface and/or sidewall roughness.
It is also desirable that such materials be hydrophobic to avoid uptake of moisture (or other fluids) once installed and in use. The hydrophobicity of a material can be measured by the contact angle made by a drop of water (having a specific volume) on the material surface. Hydrophobicity is particularly desirable for waveguides and other optical devices that are deployed in potentially high humidity environments (or other environments where the device could be exposed to water or other liquids or gases that could be absorbed by or otherwise degrade the device).
Also, it is important that the material be highly stable with a relatively high glass transition temperature (not degrade or otherwise physically and/or chemically change upon further processing or when in use). A common procedure for testing the stability of a material is the so-called “pressure cooker” test—where a material is placed in a wet environment at a particular pressure and temperature for a predetermined period of time in order to determine whether the material will degrade under such conditions. For example, the hybrid material of the invention on a substrate can be heated in supercritical water vapor at 2 atm and at 120 C. for 2 hours without degradation (e.g. after which optical absorption, polarization dependent loss and/or refractive index change remains unchanged ±5%—or preferably ±2%—and, of course, the material remains on the substrate).
Often, current materials used for making optical device components have only one or a few of the above-mentioned characteristics. For example, inorganic materials such as silica are relatively stable, have relatively high glass transition temperatures have relatively low optical loss. However, silica materials often require higher deposition temperatures (limiting substrates and components on the substrates) and have lower deposition rates and cannot be directly patterned. Organic materials such as polymers can be deposited at lower temperatures and at higher deposition rates, but are relatively unstable and have lower glass transition temperatures. What are needed are materials for optical device components that have a larger number of the preferred characteristics set forth above.
In the present invention, stable hybrid organic-inorganic materials are used for the various applications mentioned above, and others. The hybrid materials of the invention provide the benefits of inorganic materials (stability, glass transition temperature, optical profiles, etc.) while also providing the benefits of organic materials (ease of handling and deposition, etc.). Preferably, the hybrid materials of the invention have an inorganic backbone, such as one made of a metal or metalloid oxide three dimensional network, with organic substituents and cross linking groups (which call be partially or fully fluorinated).